American heart journal
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American heart journal · Jul 1994
Hemodynamic and volumetric response of the normal left ventricle to upright tilt testing.
The purpose of this study were to determine the specificity of the head-up tilt test in normal subjects when a graded isoproterenol infusion is used, and to evaluate the role of dynamic ventricular volume change during head-up tilt as a mechanism of syncope. We prospectively studied 12 normal volunteers, each of whom underwent an upright tilt test for 10 minutes at 80 degrees with and without an infusion of isoproterenol. A subgroup of five subjects had a third tilt test during administration of a combination of esmolol and isoproterenol. ⋯ Systolic blood pressure rose slightly above baseline during isoproterenol but fell from 118 +/- 4 to 85 +/- 5 mm Hg during head-up tilt with isoproterenol. The three asymptomatic subjects had only one significant change, an increase in heart rate with isoproterenol. In the five responders undergoing three tilt tests, left ventricular volume decreased significantly at end diastole (94 +/- 25 vs 58 +/- 22 ml) and end systole (34 +/- 13 vs 18 +/- 6 ml) when supine baseline is compared with initial upright tilt.(ABSTRACT TRUNCATED AT 250 WORDS)
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American heart journal · Jul 1994
Effects of low-dose flosequinan on left ventricular systolic and diastolic chamber performance.
Flosequinan (manoplax) is a new vasodilating agent for the treatment of congestive heart failure. Although it may have several mechanisms of action, whether it has effects on left ventricular inotropic or luisotropic events in hemodynamically relevant low doses when added to standard therapy for congestive heart failure is unknown. Ten patients with dilated congestive cardiomyopathy who were receiving standard therapy for heart failure were studied. ⋯ These data indicate that when flosequinan, a new therapeutic agent for the treatment of congestive heart failure, is administered in hemodynamically relevant low doses to patients with dilated congestive cardiomyopathy who were receiving standard therapy for heart failure, left ventricular pump function and diastolic function is further improved. There was, however, no significant effect on left ventricular contractility. This study emphasizes that new therapeutic agents like flosequinan, when administered in lower doses to avoid the potential deleterious effects of enhanced inotropy, may be useful additions to standard therapy in patients with congestive heart failure.
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American heart journal · Jul 1994
Is there an abnormal QT interval in sudden cardiac death survivors with a "normal" QTc?
Correcting the QT interval for heart rate may mask ventricular repolarization abnormalities and may lead to a misinterpretation of the physiologic and pathophysiologic findings. In this study the QT/R-R relationship was studied in eight sudden cardiac death (SCD) survivors without overt structural heart disease and compared with eight age- and sex-matched normal subjects. All patients were in a drug-free state. ⋯ However, the regression line of the QT interval against the R-R interval was significantly (p < 0.01) altered in SCD survivors compared with normal subjects. These observations suggest that there is abnormal ventricular repolarization (QT interval) despite an apparently normal QTc using Bazett's formula in these patients. Evaluation of the QT/R-R relationship by means of 24-hour ambulatory Holter ECG monitoring may provide a useful clinical tool for the assessment of ventricular repolarization abnormalities.